It's important to continuously monitor where students are to make sure your instruction is effective — and to flag foundational skills that haven't been mastered, which can cause problems later.
Informal assessments can be used during a lesson to ensure students are grasping the information and applying what they know.
Periodic individual assessments are also key. Here is an assessment you can use to see if students are applying their knowledge of closed syllables when reading and spelling words. (This assessment is the same as the one used for assessing short vowel knowledge.) If students can read and spell words with short vowels then they have mastered the skill of reading and spelling closed-syllable words.